Ocular examination, including gonioscopy and ultrasonographic biometry (biological measurement), was performed in healthy, purebred Samoyeds. When the dogs were subclassified according to the degree of kinship with cases of primary angle-closure glaucoma, it was found that the opening of the ciliary cleft was wider in dogs less related to dogs with primary angle-closure glaucoma than in more closely related dogs. Furthermore, multivariate analysis of the material indicated that parentage of a dog has a substantial effect on the intraocular distances studied in this investigation (relative depth of the opening of the ciliary cleft, relative corneal thickness, relative anterior chamber depth, relative lens thickness, and relative length of the vitreous body). Finally, heritability of the relative depth of the opening of the ciliary cleft was estimated at 56% and that of the common environmental factor at 19%. The results are indicative of a hereditary component in primary angle-closure glaucoma in the Samoyed breed.